Poetic euphamism: The spontaneous and audible expulsion of air from the vaginal cavity, often during fast-paced coitus. There exists a breed of women that can and will perform this phenomenon on cue.
Pitch and tone can be determined by manipulation of the pelvic floor or 'kiki' muscles.
For further reference, see also queef and fanny fart.

Girl: 'My muff guff abilities are so advanced, I've been invited to join the London Philamuffic.'